超大型浮体和调谐减振发电装置的物面非线性水弹性响应方法研究

Very large floating structure (VLFS) is commonly assembled by connecting small individual modules, and the hydroelastic response of these modules is a typical fluid-structure interaction problem. For most applications, it is desirable to reduce the deflection and stresses of the VLFS subjected to the wave action and validate the feasibility of the VLFS by employing various anti-motion devices. However, only a few papers have presented multi-body hydroelastic problems on flexible floating bodies, anti-motion devices, flexible connectors and fluid, and the linear dynamic response of interconnected multi-module structures is usually performed in the frequency domain when determining the hydroelastic response amplitude operator of the floating bodies..In terms of the foregoing situation, an innovative concept i.e. Tuned Perforated Anti-motion Plate is proposed to be an alternative solution for wave energy absorption and conversion. For the multi-body hydroelastic analysis, the coupled dynamics body nonlinear time-domain model is established to be solved by the combination of the modal expansion method, finite element method and boundary element method. In the body nonlinear time-domain model, the interpolation-tabulation scheme is utilized to assess rapidly and accurately the free-surface Green function in finite water depth, and a dynamic grid technique based on the spring analysis is applied to re-mesh the instantaneous wetted body surface. For the calculation of nonlinear wave loads, a three-point backward difference expression is introduced. Numerical calculations are conducted to obtain the hydroelastic behavior with operating conditions and different proposed survival strategies. In addition, the model experiments with the novel multi-module VLFS and wave energy absorption-conversion device combined system are also conducted in the wave basin to confirm the numerical model and results. On basis of these, the effects of plate parameters, wave parameters, and body nonlinear on the hydroelastic response of the modules and wave output power of the tuned perforated plates are systematically investigated, meanwhile, the interaction mechanism among modules, anti-motion plates and connectors is also analyzed. .The aim of this research project will further innovates the design idea of the wave energy absorption-conversion device attached to the edges of the multi-module VLFS, and expands the interaction research field of waves and traditional pontoon-type VLFS.

超大型浮式结构物 (VLFS)是一个模块化结构，其水弹性响应是一个典型的流固耦合问题。为减小波浪对各模块的影响，保证结构安全性，常在VLFS周围安装减振装置。但目前关于多柔性体、减振装置、连接器和流体的多体耦合水弹性力学研究十分少见，且主要集中在频域里的线性数值模拟。.针对此现状，本项目拟提出一种VLFS的调谐减振发电装置，采用模态展开法并联合有限元、边界元方法建立多体物面非线性的水弹性时域耦合数值模型。该模型采用造表插值技术快速估算格林函数，利用弹簧近似法生成的动网格技术更新瞬时物体湿表面网格，使用三点向后差分模式计算非线性波浪荷载。本项目研究典型工况和自存策略下结构的水弹性响应，并构建模型试验验证数值方法的正确性，在此基础上，探索结构和波浪参数、物面非线性对计算结果的影响规律以及多体之间的耦合效应。以期革新VLFS的减振发电装置设计理念，拓展波浪与传统厢式VLFS相互作用研究领域。

水弹性响应模拟对于解决超大型浮体设计的工程问题，以及研究超大型浮体及其减振装置的动力耦合效应等科学问题均起到关键作用。目前在利用水下平板减小超大型浮体水弹性响应时，均将减振平板与超大型浮体作为整体进行研究，未考虑它们之间连接方式的选择，且关于物面非线性边界条件对于多体水弹性响应的影响方面研究还处于空白，仍需进一步探索。针对此现状，本项目首先提出了一种安装于浮体迎浪端水下一定位置处的调谐透空减振发电装置，确定一体化结构的模型参数，建立了结构有限元模型求解此集成体系在空气中振动的干模态振型及自振频率；然后将干模态振型作为物面边界条件，考虑瞬时物体湿表面变化引起的非线性因素、流体一阶力对二阶成分的影响、柔性连接器和PTO约束系统的连接力，建立超大型浮体与减振发电装置的耦合动力学模型，求解得到超大型浮体在典型工况和自存策略下的水弹性响应；最后，科学构建多柔性浮体和刚性减振装置的水弹性响应模型试验，验证和完善了相关时域数值方法的准确性，达到了预期研究目标。通过本项目的实施，完整地建立了一套超大型浮体物面非线性数值分析方法，解决了物面瞬时运动对浮体水弹性响应影响的求解问题，使得数值模拟结果更加逼近真实解，成功应用于工信部、财政部联合资助重大专项《浮式保障平台工程（二期）-防浪消波专题》中双模块浮式防波堤水动力性能分析，并指导2019年南海原型海上测试分析，取得了丰富的实践成果，拓展了波浪与超大型浮体相互作用的研究领域。